eMedicine - Inner Ear, Meniere Disease, Surgical Treatment : Article by John C Li

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Inner Ear, Meniere Disease, Surgical Treatment

Article Last Updated: Jan 17, 2007

History of the Procedure

The term endolymphatic hydrops is often used synonymously with Ménière disease and Ménière syndrome. Endolymphatic hydrops refers to a condition of increased hydraulic pressure within the inner ear endolymphatic system.

Problem

Excess pressure accumulation in the endolymph can cause a tetrad of symptoms: (1) fluctuating hearing loss, (2) occasional episodic vertigo (usually a spinning sensation, sometimes violent), (3) tinnitus or ringing in the ears (usually low-tone roaring), and (4) aural fullness (eg, pressure, discomfort, fullness sensation in the ears).

Frequency

Although the frequency is probably underestimated, a reasonable estimate is approximately 1,000 cases per 100,000 people. A familial predisposition seems to exist; approximately one half of all patients have a family history of the disease.

Mortality/Morbidity: Although the disease itself is not lethal, significant morbidity can arise from various manifestations of the disease. Vertigo can cause devastating accidents and falls. Hearing loss is often progressive over time. Many patients are unable to work and are forced to claim disability.

Sex: Although sex-related rates are nearly equal, a slight female preponderance may exist, in the range of 50-65%.

Age: In some studies, the mean age among treatment groups was 49-67 years. Ménière disease has been seen at almost all ages. Typical onset begins at early-to-middle adulthood.

Etiology

The syndrome may be idiopathic or may be secondary to various processes interfering with normal production or resorption of endolymph. Examples of these processes are endocrine abnormalities, trauma, electrolyte imbalance, autoimmune dysfunction, medications, parasitic infections, and hyperlipidemia.

Pathophysiology

Two fluids fill the chambers of the inner ear: endolymph and perilymph. These fluids are separated by thin membranes, which house the nervous tissue of hearing and balance. Fluctuations in pressure of these fluids stress the nerve-rich membranes and can cause hearing disturbance, ringing in the ears, vertigo, imbalance, and a pressure sensation in the ear.

More specifically, episodes of hydrops are probably caused by an increase in endolymphatic pressure that causes a break in the membrane separating the perilymph (a potassium-poor fluid) from the endolymph (a potassium-rich fluid). The resultant chemical mixture bathes the vestibular nerve receptors, leading to depolarization blockade and transient function loss. Sudden change in the vestibular nerve firing rate creates an acute vestibular imbalance, giving the sense of vertigo.

Physical distention caused by the increase in endolymphatic pressure leads to mechanical disturbance of the otolithic organs. Because the utricle and saccule are responsible for linear and translational motion detection, rather than angular and rotational acceleration, irritation of these organs may produce nonrotational vestibular symptoms.

This physical distention causes mechanical disturbance of the organ of Corti as well. Distortion of the basilar membrane and of the inner and outer hair cells may cause hearing loss and tinnitus. Because the apex of the cochlea is wound tighter than the base, the apex is more sensitive to pressure changes than the base. This explains why hydrops affects low frequencies (located at the apex) more than high frequencies (located at the relatively wider base of the cochlea).

Symptoms improve after the membrane is repaired and normal sodium and potassium concentrations are restored.

Clinical

The typical history involves episodic attacks of true whirling vertigo. These attacks are usually preceded by a variable sense of ear pressure and fullness; decreased hearing; and a low-tone, roaring tinnitus. Episodes of vertigo usually last minutes to hours and are often associated with severe nausea and vomiting. In general, patients feel "run down," imbalanced, and nauseated for several hours to days after an acute attack.

The timing and frequency of the attacks vary. Some patients can regularly predict when they will have an attack. Others note a completely random pattern. Attacks have been linked to triggers such as foods, menstrual cycles, and psychosocial stress.

Some patients are completely asymptomatic between episodes. However, many notice progressive deterioration of hearing and balance function with each successive attack.

Results of the physical examination vary depending on the disease phase. Physical examination results may be completely normal during remission, particularly if the patient is asymptomatic.

During an acute attack, patients generally have severe vertigo and are often in significant distress. Many present to the physician's office with signs of recent vomiting. Patients are occasionally diaphoretic and pale. Vital signs may show elevated blood pressure, pulse, and respiration.

Neurotologic examination may reveal significant nystagmus. Pneumo-otoscopy of the affected ear may elicit symptoms or cause nystagmus. Generally, the Romberg test (ie, observation of sway or loss of balance while the patient is standing with his or her eyes closed) reveals significant increase in instability and worsening with the eyes closed. If the patient is able to stand with his or her eyes closed, the Fukuda marching step test (ie, observation of directional drift while the patient is marching with eyes closed) may reveal significant deviation. The Dix-Hallpike test (ie, observation of nystagmus while moving a patient from sitting to supine with the head angled 45° to 1 side and then the other) may be positive, indicating coexisting benign positional vertigo.

Hearing is frequently affected. The Weber tuning fork test usually shows results lateralized away from side of the affected ear. In general, the Rinne test indicates that air conduction remains better than bone conduction.

Performing a complete neurologic evaluation during the physical examination is important. New-onset vertigo may be an early sign of stroke, migraine, or brainstem compression, which require emergency care vastly different from those of Ménière disease.

Surgery is indicated for Ménière disease that is refractory to medical management. Typically, failure to respond to 3-6 months of medical therapy is an indication of surgery. However, patients with severe debility may undergo surgery sooner. Any underlying medical causes for Ménière disease should be treated before surgical therapy is undertaken. The diseased ear must be clearly identified.

The relevant anatomy revolves around the petrous bone and the inner ear. The ear is divided into 3 sections: external, middle, and inner. The external ear consists of the auricle, external ear canal, and tympanic membrane. The tympanic membrane separates the external ear from the structures of the middle ear. The middle ear is an air-containing space that houses the 3 hearing bones: the malleus, the incus, and the stapes. The inner ear is completely encased in bone and consists of the cochlear vestibular apparatus and its associated nerves.

The cochlear vestibular apparatus is a complex organ arranged in a complex yet elegant spatial orientation. Because it is completely encased in bone, the organ is housed in a series of winding tunnels and interconnecting spaces. The mazelike orientation of these tunnels is appropriately named the labyrinth. The bony labyrinth is the space that encases the membranous labyrinth.

The cochlear portion is a snail-shaped organ that houses the organ of Corti. It is responsible for translating mechanical vibrations into electrical impulses and sending them to the brain through the cochlear nerve. The vestibular system consists of a large chamber (ie, vestibule), from which 3 semicircular canals protrude. Within the vestibule, 2 sensors, ie, the utricle and the saccule, detect linear acceleration, while the semicircular canals detect rotational movements in the 3 planes of rotation.

The cochlear and vestibular segments are joined in the middle and share a dual-chambered hydraulic system. These hydraulic chambers are bathed by endolymph and perilymph. A membrane (ie, membranous labyrinth) separates the fluids and completely surrounds the endolymph like a balloon.

The system may be visualized as a water balloon floating in a pool. The water balloon is the membranous labyrinth that contains the endolymph. Surrounding pool water is the perilymph, which supports the delicate nerve tissues of the membranous labyrinth. In this analogy, the walls of the pool represent the limits of the bony labyrinth space. The ground encasing the pool is the bone that encases the labyrinthine space.

The endolymphatic sac is a reservoir pouch that resides on the posterior surface of the petrous bone against the posterior fossa dura. It is connected via the vestibular duct to drain into the endolymphatic space of the cochlea.

The vestibular apparatus gives off 2 nerves: the superior and the inferior vestibular nerves. Together with the cochlear and facial nerves, the vestibular nerves travel through the internal auditory canal to the cerebellopontine angle.

Patients should be in good health and able to withstand surgery and anesthesia. Perform careful history taking and physical examination before the procedure to detect any medical contraindications.

Surgery is not necessarily contraindicated in elderly patients. Patients in their 80s have tolerated labyrinthectomy fairly well.

Otitis media and mastoiditis are contraindications for surgery. Resolve these infections before proceeding to avoid an increased risk of meningitis.

One principle of ear surgery is to avoid operating on an ear that provides all of the patient's hearing because of the risk of creating profound bilateral deafness. This rule applies to most otologic surgical procedures.

Bilateral vestibular disease is the relative contraindication for destructive procedures because of risk of complete loss of inner ear function (ie, Dandy syndrome).

Hypersensitivity or allergy to the target medication is a contraindication for aminoglycoside perfusion.

Medical therapy

Medical therapy is directed toward the mitigation of symptoms and/or their prevention.

Medical treatment of Ménière disease is tailored to the individual during the quiescent phase. Lifestyle and dietary changes are usually the first steps. Avoidance of identifiable triggers (eg, chocolate, caffeine) could be sufficient. Usually, smoking cessation is also recommended.

If medications are required, prescribe a 3-month trial of a diuretic (eg, hydrochlorothiazide and triamterene [Dyazide]) in conjunction with dietary management. Typically, vestibulosuppressants and antinausea medications (eg, meclizine [Antivert], prochlorperazine [Compazine]) are used on an as-needed basis. Chronic use of these medications can be harmful and is not recommended.

For patients with acute vertigo, treatment is directed at controlling the vertigo. Intravenous or intramuscular diazepam provides excellent vestibular suppression and antinausea effects. Steroids can be given for their anti-inflammatory effects in the inner ear. Intravenous fluid support can also help prevent dehydration and replace electrolytes.

Aminoglycosides are a class of antibiotics that were serendipitously discovered to be preferentially toxic to the vestibular (balance) end organ. Destruction of the vestibular end organ renders the brain insensitive to fluctuations in inner ear pressure brought on by Ménière disease. Given systemically, aminoglycosides affect both ears. Although aminoglycosides can be used to treat extremely severe bilateral Ménière disease, such treatment leaves the patient with little or no balance function. The resulting Dandy syndrome can be debilitating.

One recent innovation in the treatment of Ménière disease is the Meniett device. Its use is not precisely a medical treatment, and the device itself does not require surgical installation. It does, however, require insertion of tympanostomy tube so that the device can work; therefore, its use may qualify as a surgical treatment. The Meniett device delivers pulses of pressure to the inner ear via the tympanostomy tube. Although no one knows exactly why this works, some patients have symptomatic relief when the device is used on a daily basis. Because it is new, long-term results have not been fully evaluated.

Surgical therapy

Surgical management of Ménière disease is reserved for medical treatment failures. Typically, failure of a 3- to 6-month trial of diuretics and dietary control justifies a more aggressive approach. Patient factors (eg, severity, occupation, degree of disability, individual tolerance) also affect the timing of surgery.

Surgical therapy has significantly evolved over the past 30 years. In general, most experts agree that surgical therapy for Ménière disease is reserved for cases in which medical treatment fails. Beyond this, considerable controversy exists. Historically, multitudes of clever surgical procedures have been invented, tested, and discarded. This article covers the 4 most generally accepted management options: endolymphatic sac decompression or shunt placement, transtympanic medication perfusion, vestibular nerve sectioning, and labyrinthectomy.

Surgical procedures are divided into 2 major classifications: destructive and nondestructive.

The rationale for using destructive procedures to control vertigo is as follows: Endolymphatic hydrops causes fluid pressure to build up in the inner ear, causing temporary malfunction and misfiring of the inner ear. Abnormal signals traveling to the brain cause vertigo. Therefore, destruction of the inner ear or nerve prevents abnormal signals from reaching the brain. The brain eventually compensates for the loss of the damaged labyrinth, provided that the other inner ear is working properly.

Destructive procedures have several problems. The decision to destroy the function of a misfiring inner ear is predicated on the adequate function of the opposite ear. However, Ménière disease can be bilateral in 7-50% of patients, according to the literature. Therefore, the author recommends avoidance of using destructive procedures in patients with bilateral Ménière disease. Because balance and hearing are closely intertwined in the labyrinth, destruction of the balance portion poses a high risk of destroying hearing as well. Destructive procedures are irreversible and are reserved for severe cases.

Nondestructive procedures are aimed at improving the state of the inner ear. Nondestructive procedures are less invasive than destructive ones and do not preclude use of other treatment modalities.

Preoperative details

Surgeons must definitively decide which ear is affected and rule out other medical causes of Ménière syndrome before proceeding to surgery.

Appropriate laboratory tests are done to identify other problems. Surgery should proceed only after these results rule out other problems.

Electrocochleography (ECoG) can help in localizing the problematic ear. Electronystagmography (ENG) can be helpful to demonstrate reduced vestibular responses and is essential to establish vestibular function in the nonsurgical ear when a destructive procedure is contemplated.

Document function of the inner ear before surgery. Because hearing fluctuates, several preoperative audiograms may be required to capture the range of hearing function. Audiograms can help in identifying the diseased side.

After destructive procedures, patients may initially feel worse than ever and require substantial preoperative and postoperative counseling to adequately prepare for the possible sequelae.

Intraoperative details

Intraoperative monitoring of the cranial nerves is useful in endolymphatic sac surgery, labyrinthectomy, and vestibular nerve section. Most physicians routinely monitor the facial nerves in all 3 of the procedures mentioned above. Intraoperative monitoring of auditory brainstem responses (ABRs) or direct monitoring of the cranial nerve VIII is crucial for optimal hearing preservation when the vestibular nerve is sectioned. Replacement of the bone flaps in retrosigmoid nerve sections can often prevent dural traction headaches.

In theory, the endolymphatic sac procedure decreases pressure buildup of the endolymph by removing petrous bone that encases the endolymph reservoir. This allows the reservoir sac to expand more freely than before and allows the pressure to dissipate. In addition, some surgeons insert a drain or valve from the endolymphatic space to the mastoid or subarachnoid space to further reduce pressure.

Exposure of the endolymphatic sac is essentially extended mastoidectomy. Special care is taken to skeletonize the sigmoid sinus, posterior fossa dura, and posterior semicircular canal. Thin egg-shelled bone is removed from the posterior fossa dura and sigmoid sinus. The endolymphatic sac is distinguished from the dura by differences in its color and texture (ie, sac is thicker and whiter than surrounding tissue).

The location of the sac can vary somewhat, but it is generally immediately posterior or posteroinferior to the posterior semicircular canal. In endolymphatic sac decompression, the procedure is terminated all of the bone overlying the sac is removed. Shunt procedures involve incising the lateral leaf of the sac and inserting a drainage tube into the internal lumen of the endolymphatic duct. Shunts can drain into the subarachnoid space or the mastoid space.

Success rates of 60-90% have been reported for vertigo control and stabilizing hearing acuity. Success rates for endolymphatic sac decompression and for shunt procedures do not seem to differ substantially.

Morbidity and mortality risks with endolymphatic sac decompression are relatively small. The risk of hearing loss and facial nerve damage is minimal when the procedure is done by experienced surgeons. Severe postoperative pain is unusual, and the recovery period is usually short and uneventful.

The endolymphatic sac procedure is perhaps one of the most controversial issues in neurotology. Critics state that the procedure is completely worthless. Authors of the famous Danish study argue that endolymphatic surgery is as useless as sham surgery and that any benefit is a placebo effect. Proponents of sac surgery argue that patients really do improve. Compared with destructive procedures, endolymphatic sac procedures have low risk and morbidity and can provide relief to patients in whom medical therapy fails.

Transtympanic medication perfusion (see Image 1) is becoming an established treatment modality. Popularized by Dr John Shea in 1995, the procedure is still evolving. Although the techniques, insertion devices, indications, and pharmacologic compositions vary, the basic concept remains the same. Medications that may exert some effect on Ménière disease are delivered to the middle ear cavity through a myringotomy. From there, medication is absorbed into the inner ear, presumably through the round window membrane. This method facilitates the application of high concentrations of medication with minimal systemic effects.

Transtympanic medication perfusion is relatively low risk and simple to perform. Essentially, the procedure is similar to the placement of tympanostomy tubes, which can be done in an office or outpatient setting. Innovations such as the round window microcatheter and Silverstein MicroWick were designed to channel medication flow directly to the round window niche. Theoretically, this method reduces dosing inconsistencies due to loss of medication down the eustachian tube. The round window microcatheter has lost favor and is no longer being produced.

Transtympanic perfusion is considered a nondestructive procedure when steroids are used. Transtympanic steroid application is useful, particularly when patients have poor tolerance for the systemic adverse effects of steroids. Furthermore, high concentrations can be administered by using this approach. Although results of long-term studies are not yet available, success rates appear to be favorable.

Transtympanic perfusion is considered a destructive procedure when aminoglycosides are used. When aminoglycosides are given transtympanically, their effects are concentrated in the affected ear rather than in both ears. Because streptomycin is difficult to obtain in the United States because of restrictions by the U.S. Food and Drug Administration (FDA), gentamicin is more widely used. Early studies show an efficacy of about 90%. Some authors report substantial worsening of hearing in 5-25% of patients.

Sectioning the diseased balance nerve can be the ultimate solution for patients with useful hearing in the affected ear. Although hearing and balance functions are housed in 1 common chamber within the inner ear, their neural connections to the brain separate themselves into distinct nerve bundles as they course through the internal auditory canal. This anatomical separation facilitates the isolation and ablation of balance function without disturbing hearing function.

Vestibular nerve sectioning is similar to approaches used for acoustic neuroma, because it involves the opening of the internal auditory canal. Vestibular nerve sections are typically performed through a retrosigmoid or middle fossa approach. The translabyrinthine approach would not spare hearing and is used only as added insurance when labyrinthectomy is intended.

Surgeons generally agree that the retrosigmoid approach is less technically difficult than the middle-fossa approach. The retrosigmoid approach is performed through a small craniotomy posterior to the sigmoid sinus. Exposure of the cerebellopontine angle allows visualization of the eighth cranial nerve. Proper identification of the vestibular nerve through observance of proper anatomic relationships is mandatory to avoid severing facial and cochlear nerves. Because the nerve bundle rotates as it exits the internal auditory canal, the vestibular nerve moves from its lateral position to a more superior location. The vestibular nerves are those closest to the tentorium. Monitoring of the facial and cochlear nerves by means of intraoperative ABR monitoring is helpful.

The middle-fossa approach for vestibular nerve sectioning involves creating a 5 X 5-cm craniotomy in the middle fossa just superior to the temporal line above the external ear canal. The dura of the middle fossa is retracted superiorly to expose the bone. After the proper anatomical landmarks are identified, the internal auditory canal is identified and opened, and the vestibular nerve is sectioned as laterally as possible. Fat is packed into the internal auditory canal and held in position by the temporal lobe dura. The craniotomy is then closed to terminate the procedure.

The middle fossa approach has slightly more complete ablation of vestibular function. Because the vestibular fibers are cut immediately as they exit the vestibular and organ, stray vestibular fibers have little opportunity to cross over and travel along the facial and cochlear nerves. The vestibular nerve is sectioned much more medially in the retrosigmoid approach, possibly after stray vestibular fibers have crossed. Although unusual, failure of the retrosigmoid approach may be attributed to these crossed fibers.

Difficulty of locating the internal canal and limited exposure in the canal because of the position of the facial nerve are disadvantages of using the middle-fossa approach. Cutting the vestibular nerve without exerting pressure on cochlear and facial nerves is difficult because the vestibular bundle lies deep within the canal. Furthermore, the risk of damaging the cochlear artery, which causes hearing loss, is higher via the middle fossa than the retrosigmoid approach.

Advantages of vestibular nerve sectioning are a vertigo-control rate of about 95-98%, and hearing preservation in the surgically treated ear, which is successful in about 95% of patients. Risks of this procedure are those inherent to craniotomy and acoustic neuroma surgery. Facial-nerve damage, hearing loss, exacerbation of tinnitus and dizziness, CSF leakage, headaches, hemorrhage, and infection (meningitis) are possible but rarely develop.

After surgery, patients generally require 3-5 days of inpatient care. Adaptation to the surgical loss of 1 vestibular apparatus usually takes weeks to months. Vestibular rehabilitation during this period is often helpful.

Labyrinthectomy has the advantage of a high cure rate (>95%) and is useful in patients in whom Ménière disease has destroyed their hearing on the affected side. Labyrinthectomy involves ablation of the diseased inner-ear organs but does not require entry into the cranial cavity. Therefore, it is less complex than vestibular nerve sectioning.

Labyrinthectomy can be accomplished through 2 approaches: transcanal and basic mastoidectomy. The transcanal approach takes place through the external ear canal. First, a tympanomeatal flap is elevated. Next, a right angle pick is inserted through the oval window and maneuvered to disrupt and scramble the nerve tissues of the labyrinth. Sometimes, a drill is used to connect the round and oval windows to improve exposure to the neuroepithelium.

Labyrinthectomy can also be performed with a basic mastoidectomy approach. Extension of the mastoidectomy by drilling through the semicircular canals allows for more complete ablation of the labyrinthine neuroepithelium than does the transcanal approach.

Labyrinthectomy is a bit less invasive than vestibular nerve sectioning. Craniotomy is not required; therefore, the risk of CSF leakage and meningitis is reduced. Patients typically require a few days of inpatient care. Adaptation to the surgical loss of 1 vestibular apparatus usually takes weeks to months. Vestibular rehabilitation during this period is also helpful.

Image 2 shows an intraoperative view of a left ear treated with labyrinthectomy.

Postoperative details

Postoperative care is different for each of the surgeries. Patients undergoing destructive surgery can expect severe vertigo and imbalance for the first few days. Liberally dispense medications to alleviate nausea and vomiting during this time. Early vestibular rehabilitation is helpful in achieving rapid compensation for loss of unilateral vestibular input.

Follow-up

In general, outpatient follow-up requires substantial supportive care. Patients are often dizzy and report feeling worse than ever before. Outpatient vestibular rehabilitation has been helpful in patients undergoing destructive procedures.

Patients who have undergone endolymphatic sac decompression notice conductive hearing loss due to blood that accumulates behind the eardrum after surgery. Some patients have dizziness immediately after surgery.

Long-term follow-up can be scheduled for every 3-6 months initially and then changed to an as-needed schedule.

Many potential risks and complications exist, but they develop relatively rarely. As with any ear surgery, hearing loss, tinnitus, dizziness, facial paralysis, hematoma, bleeding, CSF leak, taste disturbance, and mouth dryness are possible.

Transtympanic injections are the least risky treatments among those discussed here. Transtympanic injections are equivalent to tympanostomy tube placement in terms of risk. Risks vary with the type of medication applied. Steroids have been fairly safe when given transtympanically. Aminoglycosides can adversely affect hearing. Hearing loss statistics range from 5-25%. Some authors have noted otitis media, otorrhea, and prolonged perforations.

Endolymphatic sac decompression incurs the same risks as standard mastoidectomy does. Endolymphatic sac shunts can increase the risk of CSF complications (eg, leakage, meningitis) when they penetrate the subarachnoid space.

Vestibular nerve sectioning involves craniotomy and therefore carries the highest risk of CSF complications and increases the risk of damage to the facial and cochlear nerves compared with standard mastoidectomy. Other complications depend on the approach used. The retrosigmoid approach is associated with a high incidence of traction headaches, which has been attributed to postoperative adhesion of the scalp to the dura, particularly when the bone window is not replaced. Violation of the tracts of the labyrinthine air cells can also be a pathway for CSF leakage if these openings are not covered with bone wax.

The prognosis of patients with surgically treated Ménière disease varies with the treatment. Endolymphatic sac surgery controls vertigo in 60-90% of patients, it has a low risk of hearing loss, and it can improve the patient's hearing over time.

Destructive surgeries (eg, labyrinthectomy, vestibular nerve sectioning) have success rates of about 95-98%. However, destructive surgeries have a greater risk of hearing impairment.

Transtympanic injection of medications is a relatively new surgical approach and still being evaluated. Success rates near 90% have been reported.

The future of Ménière treatment lies in the use of methods that are less invasive and less destructive than current ones to control vertigo. The concept of transtympanic delivery of medications is appealing. As new medications and delivery systems are discovered, more refined approaches to a cure may evolve.

Inner Ear, Meniere Disease, Surgical Treatment

AUTHOR AND EDITOR INFORMATION

INTRODUCTION

History of the Procedure

Problem

Frequency

Etiology

Pathophysiology

Clinical

INDICATIONS

RELEVANT ANATOMY

CONTRAINDICATIONS

TREATMENT

Medical therapy

Surgical therapy

Preoperative details

Intraoperative details

Postoperative details

Follow-up

COMPLICATIONS

OUTCOME AND PROGNOSIS

FUTURE AND CONTROVERSIES

MULTIMEDIA

REFERENCES